Bone screws are used in various ways in osteosynthesis, for example, for setting bone fragments, as compression screws or for fixing bone fragments.
A bone screw with two axially terminal threaded segments and a middle threadless segment is known from U.S. Pat. No. 5,019,079 to Ross. The diameter of the middle segment corresponds essentially to the external diameter of the external thread at the distal threaded segment, but is larger than the core diameter of the external thread at the proximal threaded segment, so that the middle segment can be used for laterally stabilizing the two bone fragments of the fracture. It is a disadvantage of this construction of bone screws that the two external threads have different pitches, so that the different steps for the implantation, the setting the bone fragments, the compression of the bone fragments and the recessing of the screw head cannot be carried out separately from one another.
The invention is to provide a remedy to this problem. It is an object of the invention to create a bone screw, which enables the bone fragments to be set and compressed and the screw head to be recessed separately during the implantation.